1. Field of the Invention
The present invention relates to a power unit for a vehicle with an internal combustion engine for transmitting the power of the internal combustion engine to the wheels of the vehicle through a static oil hydraulic type non-stage transmission.
2. Description of the Related Art
Power units for vehicles are known. For example, Japanese Patent Laid-open No. Hei 9-183393 discloses a power unit for a vehicle in which a static oil hydraulic type non-stage transmission including a swash plate type oil hydraulic pump and a swash plate type oil hydraulic motor that is comparatively small in weigh and size, and capable of non-stage speed change.
In the power unit described in Japanese Patent Laid-open No. Hei 9-183393, a crankshaft is disclosed on the downward extension of the cylinder center axis directed substantially in the vertical direction, and the axis of the transmission and the axis of a speed change drive shaft are disposed on a line making an acute angle with the crankshaft, in relation to the downward extension of the cylinder center axis. Therefore, the speed change drive shaft bulges to a lateral side of the internal combustion engine, and the left-right dimension is enlarged. This can decrease the mountability of the power unit on the vehicle body.
On the other hand, in a power unit for a vehicle with an internal combustion engine as described in Japanese Patent Laid-open No. 2001-343060, a static oil hydraulic type non-stage transmission is disposed on either one of the left and right sides of an internal combustion engine having a cylinder center axis directed substantially in the vertical direction, and a speed change drive shaft is disposed on the outer lateral side of the internal combustion with the static oil hydraulic type non-stage transmission therebetween. Therefore, again, the size in the left-right direction of the power unit is enlarged, so that it is difficult to mount the power unit on the vehicle body in a compact fashion.
Moreover, in the power unit described in Japanese Patent Laid-open No. 2001-343060, a speed sensor for detecting the speed change ratio of the static oil hydraulic type non-stage transmission is disposed on the upper side of the static oil hydraulic type non-stage transmission. Therefore, it has been difficult to easily perform maintenance and inspection of the speed change ratio sensor, due to interference caused by a fuel tank, a seat or a vehicle body cover disposed on the upper side of the power unit.
The present invention overcomes the above-mentioned difficulties in the prior art.